Lighting device



Sept. 5, 1933. H J. sPANNl-:R ET AL LIGHTING DEVICE Filed Apr1` 50. 1929 "van gmini/11110011111011111111.:1u/rn nu Zia , INVENTORS v pafmer Patented Sept. 5, 1933v UNITED STATES LIGHTING DEVICE 11ans J. Spanner,v Berlin, Germany, and Ulrich y Deering, New York, N. Y., assignors, by mesne assignments, to said Hans J. Spanner Application April 30, 1929, Serial No. 359,329, and in Germany September 21, 1928 s claims.

This invention relates to gas discharge de-v vices, particularly to tubes that are used for lighting purposes and are operated directly from an ordinary low voltage supply circuit. One of the diiiculties commonly experienced with such devices is in igniting them, that is, -in starting the discharge between the electrodes which are spaced a considerable distance apart. It is one of the objects of the present invention to provide improved means for starting or ligniting such lighting devices which shall be simple in construction and operation, dependable in action, and not likely to get out of order.

In order to more clearly explain the invention, reference is made to `the following description of different embodiments thereof taken in connection with the following drawing, in which Fig. 1 is a longitudinal section of a gas discharge device, the external connections being shown in diagrammatic form;

Fig. 2 is a longitudinal section of another form of gas discharge device; and

FigfB is a longitudinal section of still another form of a gas discharge device.

The reference character 11 indicates a glass container or tube having electrodes 12 and 13 positioned in each end thereof. The electrode 12 may be in the form of a helix of wire having an emitting coating and may be provided with leading-in wires 14 and 15. The electrode 13 may be of similar construction 'and may be provided with leading-in wires 16 and 17.. Suitable means may be provided for furnishing a conductive path from one end of the tube to the other, suchas a wire helix 18, which has leading-in wires 19 and 2O at the respective ends thereof. The leadingin wires 14 and 19 are connected together and? to a conductor 21 which is connected to some suit-` able source of supply not shown, and in which there is connected a current limiting impedance 22. The leading-in wires 17 and 20 are also connected together and to a conductor 23 which is connected to the other side of the source of supr ply from that towhich the conductor 21 is conis only a sma :.racticnvof the current employed y for theoperation of the gaseous discharge path and the energy consumed therein is relatively- 1 middle of the conductive connection and more small. The material used for the lament or helix 18 is preferably of such a character that it will not be readily disintegrated by ionic bombardment, examples of such material being tungsten wire coated with aluminum or beryllium or compounds thereof. It is also desirable that the conductive connection between the two ends of' the tube should be emissive and for this purpose a coating may be provided of one of the strong electropositive metals such as of the alkali or alkali-earth groups or compounds thereof. It has been found possible to employ such highly active metals as caesium, rubidium, potassium and. barium. The connecting lament may also be activated by loading it with hydrogen. Such coatings may have associated therewith an amphoteric oxide such as aluminum oxide or zirconium oxide which renders such emissive substances highly resistive to ionic bombardment or disintegration.

In operation, the current flows through each lof the electrodes 12 and 13 heating them and producing an electronic emission. The relatively low supply voltage of 110 volts or 220 volts, however, does not readily start the discharge between the two electrodes. But as the emissive material` on the helix 18 is heated and the emission along this conductive path is produced the discharge is readily started between one of the `electrodes and the adjacent portion of the helix 18 and thereafter the discharge extends throughout the entire length of vthe tube. y

In the form shown in Fig. 2 the conductive con-I neetion between the two ends of the tube is in the form of a metallic strip folded or bent in 'a zigzag form and preferably touching the tube 11 at only a few points as 31 and 32. The external connections and other details of construction may be as shown in Fig. l. y In Fig. 3 a glass container or tube V11a may be provided with bends 11b and 11e and laterally extending end portions 11d and 11e in which are positioned the electrodes l2 and 13. The conductive connection between the two ends of the tube may comprise a middle portion 18a bent in a zigzag form and end portions 18h and 18e in the form of helixes so that the potential drop near the ends of thetube is much greater than in the nearly corresponds with the drop of potential throughout the gaseous discharge path during stable operation of the tube. The portion 18a, is preferably supported at relatively few parts ci the tube as at 18d and 18e near the bends'of the tube. By thus increasing the potential drop of no .vided for the emissive coatings.

the filament near the ends of the tube it is possible to start an arc more readily near the electrodes because of the shorter distance over which the' potential drop to the filament is concentrated.

In the foregoing description the conductive connection is a metallic filament or wirev but it may also be in the form of a metallic strip or deposit on the Walls of the glass. In place of emissive coatings on the filament which carries ciently to increase the electron density at the surface to a suitable degree when the molecules which strike the surface of the conductive connection will become charged by virtue of a clinging electron or electrons. Also the ions which are driven against the surface set free secondary electrons if the velocity of the ions is suiciently high, say corresponding to 10 to 20 volts. As a practical matter, the main discharge usually takes place before the conductive connection comes to a red glow.

We claim:

1. A gas discharge device comprising a container, a plurality of electrodes positioned therein, and a thin strip of electrically conductive material connecting said electrodes, said conductive material being in the spiral form adjacent to the electrodes and having a zig-zag form at points intermediate said spiral form whereby said strip is supported at relatively few points against the sides of the container.

2. A gas discharge device comprising a container, a plurality of thermionic electrodes positioned therein and a thin strip of electrically conductive material connecting said electrodes, the surface of said strip' comprising a highly emissive oxide of alkali earth.

3. A gas discharge device comprising a container, a plurality of electrodes positioned therein, and a thin stripl of electrically conductive material connecting said electrodes, the resistance .of

said strip being of a higher order near at least one electrode than on the rest of its length.

HANS J. SPANNER. ULRICH DOERING. 

